class LineItem:

    def __init__(self, description, weight, price):
        self.description = description
        self.weight = weight
        self.price = price

    def subtotal(self):
        return self.weight * self.price


if __name__ == '__main__':
    raisins =LineItem('Golden raisins',10,6.95)
    print(raisins.subtotal())
    raisins.weight = -20
    print(raisins.subtotal())